In a conventional solar cell, an n type diffusion layer is formed on the surface of a p type semiconductor substrate, a light receiving surface electrode with a herringbone pattern is formed on the front surface side, a back surface electrode is formed on the back surface side, and the overall device is constructed as a flat-plate panel structure. In such a flat-plate solar cell panel, when the angle of incidence of sunlight increases in the morning and evening, the proportion of reflected light increases, and the proportion of light that enters the panel drops.
Conventionally, therefore, various types of solar cell panels using solar cells comprising spherical semiconductor elements with a diameter of approximately 1 to 2 mm have been proposed. For example, in WO 98/15983, the present applicant proposed a solar cell and light emitting device comprising spherical semiconductor elements. In such devices, each spherical semiconductor element is provided with a diffusion layer, a pn junction and a pair of electrodes which are disposed on both ends of the semiconductor element with the center thereof interposed therebetween. Numerous solar cells of the abovementioned type are disposed in the form of a matrix having numerous rows and numerous columns, these solar cells are connected in series and parallel, and the cells are sealed in embedded form with a transparent synthetic resin, thus forming a solar cell panel. Since a pair of electrodes are formed on both ends, these solar cells are advantageous in the series connection of a plurality of solar cells; the arrangement of a plurality of solar cells in the form of a matrix, and the connection of these numerous solar cells in series and parallel, cannot be easily accomplished.
For example, the present applicant attempted series and parallel connections by disposing a plurality of solar cells in matrix form in a sandwich type configuration between two printed boards.
In this case, however, since numerous electrodes must be connected with a plurality of solar cells precisely positioned on a printed board, and numerous electrodes must be connected with another printed board superimposed on top of this assembly, the structure of the solar cell panel becomes complicated; furthermore, the size of the panel is increased, and the cost of parts and cost of assembly are increased, so that the manufacturing cost of the solar cell panel is increased.
Here, panels with various types of structures have been proposed as solar cell panels in which numerous spherical solar cells are disposed in the form of a matrix.
A solar cell panel in which numerous solar cells are connected in parallel via two sheets of aluminum foil is proposed in Japanese patent laid-open publication No. 6-13633.
In the solar cell panel (or solar cell sheet) described in Japanese patent laid-open publication No. 9-162434, a mesh is constructed from insulating warp filaments and first and second woof filaments on which different metal coating films are formed; furthermore, numerous spherical elements in which a diffusion layer is formed on the surface of a p type spherical single crystal silicon particulate are manufactured, these spherical elements are disposed in the respective eyes of the abovementioned mesh, the first woof filaments are connected to the diffusion layers, the second woof filaments are connected to the spherical single crystal silicon particulate, and these particulates are sealed by means of a synthetic resin.
In the case of this solar cell panel, the manufacture of the mesh having a special structure is not easy, and the manufacturing cost is also high; however, a solar cell panel (or solar cell sheet) can be manufactured continuously and inexpensively by means of an automated apparatus.
In the optical power generating panel described in Japanese patent laid-open publication No. 2001-210834, numerous spherical elements in which a diffusion layer is formed on the surface of a p type or n type spherical crystalline silicon particulate are manufactured, these spherical elements are inserted into numerous holes formed in a printed board, printed wiring is connected to the diffusion layers of the numerous spherical elements, the diffusion layers of the numerous spherical elements are then removed by etching on the back surface side of the printed board, the printed board in which the numerous spherical elements are incorporated is placed on top of another printed board, and the spherical crystals of the respective spherical elements are connected to the printed wiring. In this optical power generating panel, since numerous spherical power generating elements are connected in parallel, the electromotive force of a single optical power generating panel cannot be increased, and since two printed boards are used, the cost of parts and the assembly cost are high, so that the manufacturing cost of the optical power generating panel is also increased. Since two printed boards are used, the rigidity of the panel tends to be high, so that it is difficult to construct a flexible optical power generating panel. In all of the abovementioned devices, the spacing between electrodes becomes smaller as the spherical diameter is reduced, so that a reduction in size is hindered.
Objects of the present invention are to provide a light receiving or light emitting panel in which numerous spherical semiconductor elements, each of which has a pair of electrodes facing each other across the center, are electrically connected by means of a single printed wiring sheet, to provide a light receiving or light emitting panel that possesses flexibility, to provide a light receiving or light emitting panel that can be constructed as a thin type panel with a simple structure, and to provide a light receiving or light emitting panel in which the numerous spherical semiconductor elements can be connected by a desired connecting system selected from series connection, parallel connection and series-parallel connection.